The present invention relates to improvements in the ventilation of rotor rim-ventilated generators, particularly hydrogenerators of sizes greater than about 50 Mw, although the invention is not limited thereto.
Windage losses in such generators account for approximately 30 percent of the total losses contributing to the inefficiency of the machine. By reducing the windage losses a net gain in efficiency can be realized. In addition to providing a sizable reduction in windage losses, the instant invention also enables regulation of the coolant gas flow through the machine. The invention is applicable both to self-ventilating generating units and those which require external blowers for ventilation.